You won't damage the engine if you don't replace it. But the fix may be cheaper than $400. Pull the pump out (see www.volvospeed.com for info on DIY), power it and see if it still runs. If it runs then remove check valve and try to blow air through it. It it leaks, replace it ($120 in parts). Try the archives as there was a post on pump repair. BTW, I had the same problem last winter and had to replace the valve. Pump was still OK but to avoid future flooding I drilled 1/8 dia hole at the bottom of its housing to drain any condensate.
Good luck.